Local charges in involution and hierarchies in integrable sigma-models

Integrable σ-models, such as the principal chiral model, ℤT-coset models for T∈ℤ≥2 and their various integrable deformations, are examples of non-ultralocal integrable field theories described by (cyclotomic) r/s-systems with twist function. In this general setting, and when the Lie algebra 픤 underlying the r/s-system is of classical type, we construct an infinite algebra of local conserved charges in involution, extending the approach of Evans, Hassan, MacKay and Mountain developed for the principal chiral model and symmetric space σ-model. In the present context, the local charges are attached to certain `regular' zeros of the twist function and have increasing degrees related to the exponents of the untwisted affine Kac-Moody algebra 픤ˆ associated with 픤. The Hamiltonian flows of these charges are shown to generate an infinite hierarchy of compatible integrable equations

Research at RMA in the Evolving Context of Mine Action

The purpose of this chapter is to put the research of the Royal Military Academy (RMA) in mine action in a historical perspective by providing some background information. The vocabulary used in mine action and the landmine contamination problem are first presented. Formalisation of close‐in detection and of area reduction is then proposed. An overview of the research projects, the involved partners and the objectives as well as the list of PhDs performed at RMA are then provided. The chapter ends with an overview of the book and their link with the cited projects

A unifying 2d action for integrable σ-models from 4d Chern-Simons theory

In the approach recently proposed by K. Costello and M. Yamazaki, which is based on a four-dimensional variant of Chern-Simons theory, we derive a simple and unifying two-dimensional form for the action of many integrable $\sigma$-models which are known to admit descriptions as affine Gaudin models. This includes both the Yang-Baxter deformation and the $\lambda$-deformation of the principal chiral model. We also give an interpretation of Poisson-Lie $T$-duality in this setting and derive the action of the $\mathsf{E}$-model.Comment: 37 page

Efficient computation of condition estimates for linear least squares problems

Linear least squares (LLS) is a classical linear algebra problem in scientific computing, arising for instance in many parameter estimation problems. In addition to computing efficiently LLS solutions, an important issue is to assess the numerical quality of the computed solution. The notion of conditioning provides a theoretical framework that can be used to measure the numerical sensitivity of a problem solution to perturbations in its data. We recall some results for least squares conditioning and we derive a statistical estimate for the conditioning of an LLS solution. We present numerical experiments to compare exact values and statistical estimates. We also propose performance results using new routines on top of the multicore-GPU library MAGMA. This set of routines is based on an efficient computation of the variance-covariance matrix for which, to our knowledge, there is no implementation in current public domain libraries LAPACK and ScaLAPACK

Évaluation des performances d'adsorption d'un système de captage direct du CO2 avec lits mobiles

Le réchauffement climatique est proportionnel aux émissions mondiales de dioxyde de carbone dans l’atmosphère. Si aucune action réelle n’est entreprise, ces émissions pourraient atteindre 72 gigatonnes par année d’ici 2060, soit 60 gigatonnes de plus que l’objectif fixé par l’Accord de Paris sur le climat. L’objectif en question est d’atteindre une carboneutralité d’ici 2070 afin de maintenir le réchauffement climatique sous la barre des 2 °C par rapport à l’époque préindustrielle. Pour l’atteindre, la réduction des émissions ne sera pas suffisante. Il faudra impérativement capter le CO2 directement de l’atmosphère, et ce, dès 2030. Ce projet de recherche repose sur le captage direct du CO2 par adsorption solide à basse température, phénomène de transfert de masse où un adsorbat gazeux se fixe à la surface d’un adsorbant solide. Cette méthode de captage est d’ailleurs la plus viable commercialement par rapport au captage direct par absorption, avantage non négligeable dans un monde où l’implantation de marchés et de taxes sur le carbone est de plus est plus répandue. Le but de cette maîtrise est d’appliquer cette méthode de captage à un procédé utilisant une configuration à lits mobiles. Cette configuration se base sur le mouvement de multiples cellules d’adsorbant en phase d’adsorption et optimise leur cycle de service dans un écoulement contenant du CO2. Cela permet à la fois de diminuer la quantité de matériau nécessaire et de créer un cycle d’adsorption continu. Le présent rapport est une présentation du travail complété permettant de répondre à la question de recherche suivante :Quel est le gain en performance d’adsorption de dioxyde de carbone d’un système d’adsorption, par cyclage de cellules mobiles d’un matériau adsorbant poreux solide à grande échelle, par rapport à un système d’adsorption par cyclage d’un lit fixe, pendant 24 heures d’opération continue ? Le matériau adsorbant en question est un gel de silice fonctionnalisé au polyéthylèneimine. Il a été choisi pour son faible coût d’acquisition et ses performances d’adsorption. Le gain maximal obtenu pour le système par cyclage de cellules mobiles évalué est de 2.57. Ce système aurait 8 cellules mobiles au total, dont 5 se trouveraient dans le réacteur d’adsorption en tout temps. La quantité de matériau adsorbant utilisée par cellule est équivalente au 1/32 de celle qui serait utilisée pour une seule cellule fixe. Pour une même quantité de CO2 capté, cela engendre une réduction de 61 % de la masse de matériau nécessaire avec le système à lits mobiles. Si aucune contrainte de conception et d’opération n’est considérée, un gain maximal est obtenu en utilisant 2 cellules contenant le moins de matériau possible avec un temps de cycle complet (adsorption et régénération, avec ou sans échange de chaleur) le plus court possible

Bistable auto-aggregation phenotype in Lactiplantibacillus plantarum emerges after cultivation in in vitro colonic microbiota

Background Auto-aggregation is a desired property for probiotic strains because it is suggested to promote colonization of the human intestine, to prevent pathogen infections and to modulate the colonic mucosa. We recently reported the generation of adapted mutants of Lactiplantibacillus plantarum NZ3400, a derivative of the model strain WCFS1, for colonization under adult colonic conditions of PolyFermS continuous intestinal fermentation models. Here we describe and characterize the emerge of an auto-aggregating phenotype in L. plantarum NZ3400 derivatives recovered from the modelled gut microbiota. Results L. plantarum isolates were recovered from reactor effluent of four different adult microbiota and from spontaneously formed reactor biofilms. Auto-aggregation was observed in L. plantarum recovered from all microbiota and at higher percentage when recovered from biofilm than from effluent. Further, auto-aggregation percentage increased over time of cultivation in the microbiota. Starvation of the gut microbiota by interrupting the inflow of nutritive medium enhanced auto-aggregation, suggesting a link to nutrient availability. Auto-aggregation was lost under standard cultivation conditions for lactobacilli in MRS medium. However, it was reestablished during growth on sucrose and maltose and in a medium that simulates the abiotic gut environment. Remarkably, none of these conditions resulted in an auto-aggregation phenotype in the wild type strain NZ3400 nor other non-aggregating L. plantarum, indicating that auto-aggregation depends on the strain history. Whole genome sequencing analysis did not reveal any mutation responsible for the auto-aggregation phenotype. Transcriptome analysis showed highly significant upregulation of LP_RS05225 (msa) at 4.1–4.4 log2-fold-change and LP_RS05230 (marR) at 4.5–5.4 log2-fold-change in all auto-aggregating strains compared to non-aggregating. These co-expressed genes encode a mannose-specific adhesin protein and transcriptional regulator, respectively. Mapping of the RNA-sequence reads to the promoter region of the msa-marR operon reveled a DNA inversion in this region that is predominant in auto-aggregating but not in non-aggregating strains. This strongly suggests a role of this inversion in the auto-aggregation phenotype. Conclusions L. plantarum NZ3400 adapts to the in vitro colonic environment by developing an auto-aggregation phenotype. Similar aggregation phenotypes may promote gut colonization and efficacy of other probiotics and should be further investigated by using validated continuous models of gut fermentation such as PolyFermS

1,3-Propanediol dehydrogenases in Lactobacillus reuteri: impact on central metabolism and 3-hydroxypropionaldehyde production

<p>Abstract</p> <p>Background</p> <p><it>Lactobacillus reuteri </it>metabolizes glycerol to 3-hydroxypropionaldehyde (3-HPA) and further to 1,3-propanediol (1,3-PDO), the latter step catalysed by a propanediol dehydrogenase (PDH). The last step in this pathway regenerates NAD⁺and enables therefore the energetically more favourable production of acetate over ethanol during growth on glucose.</p> <p>Results</p> <p>A search throughout the genome of <it>L. reuteri </it>DSM 20016 revealed two putative PDHs encoded by ORFs lr_0030 and lr_1734. ORF lr_1734 is situated in the <it>pdu </it>operon encoding the glycerol conversion machinery and therefore likely involved in 1,3-PDO formation. ORF lr_0030 has not been associated with PDH-activity so far. To elucidate the role of these two PDHs, gene deletion mutant strains were constructed. Growth behaviour on glucose was comparable between the wild type and both mutant strains. However, on glucose + glycerol, the exponential growth rate of Δlr_0030 was lower compared to the wild type and the lr_1734 mutant. Furthermore, glycerol addition resulted in decreased ethanol production in the wild type and Δlr_1734, but not in Δlr_0030. PDH activity measurements using 3-HPA as a substrate revealed lower activity of Δlr_0030 extracts from exponential growing cells compared to wild type and Δlr_1734 extracts.</p> <p>During biotechnological 3-HPA production using non-growing cells, the ratio 3-HPA to 1,3-PDO was approximately 7 in the wild type and Δlr_0030, whereas this ratio was 12.5 in the mutant Δlr_1734.</p> <p>Conclusion</p> <p>The enzyme encoded by lr_0030 plays a pivotal role in 3-HPA conversion in exponential growing <it>L. reuteri </it>cells. The enzyme encoded by lr_1734 is active during 3-HPA production by non-growing cells and this enzyme is a useful target to enhance 3-HPA production and minimize formation of the by-product 1,3-PDO.</p

Inhibitory activity spectrum of reuterin produced by Lactobacillus reuteri against intestinal bacteria

<p>Abstract</p> <p>Background</p> <p>Reuterin produced from glycerol by <it>Lactobacillus reuteri</it>, a normal inhabitant of the human intestine, is a broad-spectrum antimicrobial agent. It has been postulated that reuterin could play a role in the probiotic effects of <it>Lb. reuteri</it>. Reuterin is active toward enteropathogens, yeasts, fungi, protozoa and viruses, but its effect on commensal intestinal bacteria is unknown. Moreover reuterin's mode of action has not yet been elucidated. Glutathione, a powerful antioxidant, which also plays a key role in detoxifying reactive aldehydes, protects certain bacteria from oxidative stress, and could also be implicated in resistance to reuterin.</p> <p>The aim of this work was to test the activity of reuterin against a representative panel of intestinal bacteria and to study a possible correlation between intracellular low molecular weight thiols (LMW-SH) such as glutathione, hydrogen peroxide and/or reuterin sensitivity. Reuterin was produced by <it>Lb</it>. <it>reuteri </it>SD2112 in pure glycerol solution, purified and used to test the minimal inhibitory (MIC) and minimal bactericidal concentrations (MBC). Hydrogen peroxide sensitivity and intracellular LMW-SH concentration were also analysed.</p> <p>Results</p> <p>Our data showed that most tested intestinal bacteria showed MIC below that for a sensitive indicator <it>Escherichia coli </it>(7.5–15 mM). Lactobacilli and <it>Clostridium clostridioforme </it>were more resistant with MIC ranging from 15 to 50 mM. No correlation between bacterial intracellular concentrations of LMW-SH, including glutathione, and reuterin or hydrogen peroxide sensitivities were found.</p> <p>Conclusion</p> <p>Our data showed that intestinal bacteria were very sensitive to reuterin and that their intracellular concentration of LMW-SH was not directly linked to their capacity to resist reuterin or hydrogen peroxide. This suggests that detoxification by LMW-SH such as glutathione is not a general mechanism and that other mechanisms are probably involved in bacterial tolerance to reuterin and hydrogene peroxide.</p

Retentissement d'une acidification du milieu sur la glycosylation membranaire de cellules épithéliales de trachée en culture

International audienceLes pluies acides representent une des formes les plus graves de la pollution atmospherique. Elles sont generees essendellement par solubilisation dans l'eau de deux gaz polluants: le S02 qui peut se transformer en acide sulfurique et le dioxide d'azote qui peut generer de l'acide nitrique. Ces acides conferent alors aux precipitations un pH moyen de 3,6 pouvant aller jusqu'a 2 et, de ce fait, contribuent a abaisser le pH de nombreux milieux biologiques. Ceux ci comprennent des ecosystemes entiers (lacs) mais egalement certains tissus humains comme les voies respiratoires. Des etudes ont montre que I'abaissement du pH pouvait jouer un role significatif dans l'alteration de certaines fonctions essentielles pour de nombreuses cellules, en particulier, les cellules epitheliales. Certaines de ces fonctions sont associees ä l'expression membranaire de structures complexes dans lesquelles la partie glucidique est primordiale et, dans ce cas, les acides sialiques sont incrimines